1. Field
The present disclosure relates generally to telecommunications, and more particularly, to systems and methods to support the handoff of a mobile communications device from one network to another in a wireless communications system.
2. Background
The demand for wireless information services has led to the development of an ever increasing number of wireless networks. CDMA2000 1x is just one example of a wireless network that provides wide area telephony and data services. CDMA2000 1x is a wireless standard promulgated by the Third Generation Partnership Project 2 (3GPP2) using code division multiple access (CDMA) technology. CDMA is a technology that allows multiple users to share a common communications medium using spread-spectrum processing. A competing wireless network that is commonly employed in Europe is Global System for Mobile Communications (GSM). Unlike CDMA2000 1x, GSM uses narrowband time division multiple access (TDMA) to support wireless telephony and data services. Some other wireless networks include General Packet Radio Service (GPRS) which supports high speed data services with data rates suitable for e-mail and web browsing applications, and Universal Mobile Telecommunications System (UMTS) which can deliver broadband voice and data for audio and video applications.
These wireless networks can generally be thought of as wide area networks employing cellular technology. Cellular technology is based on a topology in which the geographic coverage region is broken up into cells. Within each of these cells is a fixed base transceiver station (BTS) that communicates with mobile users. A base station controller (BSC) is typically employed in the geographic coverage region to control the BTSs and route communications to the appropriate gateways for the various packet-switched and circuit-switched networks.
As the demand for wireless information services continue to increase, mobile devices are evolving to support integrated voice, data, and streaming media while providing seamless network coverage between wide area cellular networks and wireless local area networks (LAN). Wireless LANs generally provide telephony and data services over relatively small geographic regions using a standard protocol, such as IEEE 802.11, Bluetooth, or the like. The existence of wireless LANs provides a unique opportunity to increase user capacity in a wide area cellular network by extending cellular communications to the unlicensed spectrum using the infrastructure of the wireless LAN.
Recently, various techniques have been employed to enable mobile devices to communicate with different wireless networks. Additional techniques have been employed to support the handoff of a mobile user as it travels from one network coverage region to another. However, quality performance may be enhanced in some instances if the decision to handoff a mobile user depends not only on the location of the mobile user, but also the quality of service of the networks.